Power operated rotary impact wrench



June 28, 1955 E. H. sHAFF POWER OPERATED ROTARY IMPACT WRENCH ssheetsfsneet 1 INVENTOR.

i 3V/sf I @Mews June /28, 19.55

y E. H. sHAl-F f 2,711,662 lPOWER OPERATED ROTARY IMPACT WRENCH :5sheets-sheet 2 AFiled om@ 29, 19554 I' INVENTOR [7*/7657/2 a/ June 28,1955 E. H. SHAFF 2,711,662

POWER OPERATED ROTARY IMPACT WRENCH- Filed Oct. 29, 1955 3 Sheets-Sheet3 United States kPatent O 2,711,662 PowER O PERATED ROTARY IMPACT WRENCHErnest H. shan, Lake worth, Fla.

Application October 29,` 1953, Serial No. 389,086 16 claims. (cl.s15z.s) i

This invention relates to improvements in a power operated rotary impactwrench. The principal objects of this invention are:

First, to providea novel impact wrench having high power and relativelylong life of its parts.

Second, to provide a novel impact wrench in which the impact member orhammer is automatically disengaged from the striker member or anvil bycamming or twisting action of thedrive connection to the hammer.

Third, to provide an impact wrench in which the impacting surfaces areengaged in a fiat plane perpendicular to the direction of movement ofthe surfaces.

Fourth, to provide a novel form of impact wrench having a hammer whichis reversible to double the useful life of the impact surfaces thereon.

Fifth, to provide an .impact wrench which operates entirely upon theinertia of the parts thereof and does not require springs or leverswhich are liable to wear out.

Sixth, to provide a highly efficient impact wrench having a relativelyfew number of parts and which can be economically and inexpensivelymanufactured and assembled.

Other objects and advantages of the invention will be apparent fromconsideration of the following description and claims. The drawings ofwhich there are three sheets illustrate'four forms of a wrench.embodying the main features of the invention.

Fig. 1 is a side elevational view, partially broken away in longitudinalcross section, of a tirst form of the wrench.

Fig. 2 is a transverse cross sectional view taken along the plane of theline z -2 in Fig. l and illustrating the parts in'impact delivering`position.

Fig. 3 is similar to Fig. 2 but illustrates the parts in hammerdisengaging position. i

Fig. 4l is similar to Fig. 2 but illustrates the parts in hammerrotating position.

Fig. 5 is an en d elevational view of the hammer shown in the previousfigures.

Fig. 6 is a side elevational view of the hammer.

Fig. 7 is an end elevational view of the drive member shown in the otherfigures.

Fig. 8 is a side elevational view, partially broken away in longitudinalcrosssection, of the drive member.

Fig. 9 is a fragmentary longitudinal cross sectional view through asecond form of the wrench.

Fig. l0 is a transverse 4cross sectional view taken along the plane ofthe line 10-10 in Fig. 9 and showing the parts in impacting relation.

, Fig. 11 is a view similar to Fig. 10 by illustrating the parts inhammer disengaged position.

Fig. l2 is similar to Figs. 10 and 1 1 but illustrates the parts inhammer rotating position. y

Fig. 13 is a fragmentary longitudinal cross sectional view through athird f ormof the wrench.

Fig. 14 is a fragmentary transverse cross sectionalrvie'w 2,711,662Patented June 28, 1955 ice Fig. 17 is a fragmentary longitudinal crosssectional view through the fourth form of the wrench.

Fig. 18 is a cross sectional view taken along the plane of the line18-18 in' Fig. 17.

Fig. 19 is an end elevational view of the drive member shown in Figs. 17and 18.

Fig. 20 is a side elevational view of shown in Fig. 19.

The form of the wrench illustrated in Figs. 13 to 16 has certainadvantages from the standpoint of manufac` turing economy and may,therefore, be considered a' preferred form of the wrench. However, allforms illustrated have highly practical and desirable operatingcharacteristics.

As is best illustrated in Fig. 1, the wrench includes a housing 1 thatencloses a suitable motor having aT shaft 2 projecting therefrom. Thehousing is provided with a handle grip 3 and a trigger 4 for controllingthe motor. Desirably the motor is of the air operated type but thedetails of the motor are unimportant Vto the present invention and aretherefore, not illustrated.

Set into the end of the housing 1 is a bearing plate 5Y provided withstepped seats 6 for the roller bearings 7 and 8. The bearing plate 5 isretained in place by a cylindrical casing 9 threaded into the housing at10. The bearing 7 rotatably supports the motor shaft while the bearing 8supports a drive member as will be described.

The outer end of the casing 9 is formed into a throat 11 and providedwith a bushing 12 for rotatably and axially supporting an anvil 13. Aflange 14 on the anvil seats on thel inner end of the bushing While thestem 15 of the anvil projects outwardly from the casing and Vis adaptedto be secured to socket elements or other tools. An inner portion 16 onthe anvil is generally cylindrical in shape and is provided with acentering recess 17 that receives the end of the motor shaft 2.

Formed along theV side of the inner portion 16 ofthe anvil is a radiallyprojecting axially extending striker rib 18 having radially disposedstriker faces on its sides. The striker rib is adapted to coact with andbe engaged by the side faces of an impact rib 19 which projects radiallyinwardly from the inner surface of a tubular hammer member 20. Thehammer member 20 embraces the inner portion 16 of the anvil and seats atits outer end against the ange 14 on the anvil. The inner end of thehammer sits against the flat plate 21 of a drive member so that thehammer may move or oscillate radially with respect to the anvil and thestriker rib 18.

The'drive member of which the plate 21 is a part includes a centralsleeve 22 which is drivingly engaged with the hexagonal end of the motorshaft 2 and is externally rotatably supported by the bearing 8. Theperiphery of the plate 21 is provided with a generally cylindricalflange 23 which rotates within the casing 9. The flange l23 embraces thehammer 20. j

ln order to drivingly connect the flange 23 of the drive member with thehammer 20 the ange 23 is provided with converging chordal surfaces 24formed by shaping the sides of the flange 23 inwardly from the oppositeends of a diameter of the flange. This forms a wedge shaped pocket inthe ange 23 and the exterior surface of the hammer 20 is provided withmating chordal surfaces 25 which permit the hammer to t snugly in thepocket formed by the chordal surfaces 24. The chordal surfaces 25 on thehammer converge away from the impact the drive member rib 19 on thehammer and are formed on the opposite side of the hammer from the rib.Thus as is shown in Fig. 2 the hammer may rest in nested drivingengagement in the pocket of the drive ange 23 until the .impact rib 19engages and vis stopped by the relatively stationary striker rib 18 onthe anvil. s

Continued relative rotation of the ange 23 ofthe drive member causes thechordal surfaces 24 on the flange to wedge or squeeze the chordalsurfaces 2S on the hammer out of the wedge pocket in the ange and movethe hammer and impact rib 19 radially out of engagement with the strikerrib 18 as is shown in Fig. 3. Further rotation of the flange 23 carriesthe hammer 20 around until the radially attened inner surface 26 on the`interior of the hammer cammingly engages the relatively stationarystriker rib 18 and draws the hammer back into seated engagement in thepocket of the ange v23. This position of the parts is illustrated inFig. 4 and continued rotation of the sleeve 23 and hammer 20 will bringthe impact -rib 19 into engagement with thestriker rib 18 for asucceeding blow on the anvil.

v The wrench will thus function to deliver repeated impact blows againstthe rib on the anvil whether or not the anvil moves appreciably. Thewrench `is therefore highly effective and the impacting surfaces thereofare not greatly subject to wear-.since they strike in parallel planesperpendicular to the path of movement of the driving member. y

The form of wrench illustrated in Figs. 9 to l2 is very similar to thatjust described. It includes the corresponding principal elements of therst form of the wrench as follows: The drive shaft 2B engages androtates a drive member 21B having an axially turned peripheral ange 23Bembracing the tubular hammer 20B. The hammer surrounds the inner portion16B of an anvil 13B and is axially retained between the drive member 21Band a ange 14B on the anvil 13B. The hammer is provided with an interioraxially extending impact rib 19B and the inner portion of the anvil isprovided with an axially extending striker rib 18B cooperative with theimpact rib. The principal differences between the two forms of thewrenchgare in the formation of the at chordal surfaces 24B on the drivemember and the corresponding chordal surfaces 25B on the hammer and inthe shape of the striker rib 18B. The chordal surfaces 24B and 25B arearranged in parallel 4relation on the drive member and hammer onopposite sides of a diametrical plane passed through the impact rib 19B.The radial movement of the hammer 20B with respect tothe anvil andvdrive member is therefore a sliding movement as compared to the tiltingcamming movement of the anvil 20 inthe frstform of the wrench. u'Illestriker rib 18B extends angularly around the inner portion of theanvilfora considerably greater distance than the corresponding strikerrib 18. As is illustrated in Figs. to 12 the striker rib 18B extends forover 90 around the inner portion 16B of the anvil. The widening of thestriker rib provides a wider two-point contact between the anvil and thehammer at the point of impact of the two members. As is shown in Fig.l() the hammer 20B will strike the anvil at 27 along the meeting sidesof the two ribs and at 28 along the .periphery of thestriker rib. Theangular widening `of the striker rib also assures the rela tivelytrailing edge of the striker rib will maintain coni' tact with theopposite side of the hammer from the impact rib as at 29 in Fig. 12 topositively hold the hammer over-in-impacting position until'theleading-edge ofthe impact 'rib' morey closely approaches the strikerimpact rib as the hammer moves radially outwardly to disengage the ribs.

The form of the wrench .illustrated in Figs. 13 to 16 includes a driveshaft 2C and anvil 13C that are similar to the corresponding parts inthe previous forms of the wrench. The inner portion 16C of the anvil isprovided with a similar striker rib 18C. The hammer 20C differs from theprevious hammers in "that it may have a circular cylindrical f contourthat is easily formed into 4a single turning operation. Interiorly thehammer 20C is provided with the same 4impact rib 19C as in `the otherforms of the wrench. The drive member is conveniently made in two partsand -consists of an inner flanged coupling 22C machined to t-thehexa'gonal en'd'of `the drive shaft and a stamped plate 21C havingaxially turned parallel flanges 23C at its ends. The stamping 21C isspot welded to the coupling as at 31.

The ends, of the cylindrical hammer 20C are provided with parallelchordal slotsZSC'correspondingy in function to the chordal surfaces 25and 25B in the first two forms of the hammer. The slots at one end ofthe hammer rotatably driv'ingly and slideably receive the axiallyextending anges 23C on the drive member so that the hammer will functionin all yrespects in the same manner as the hammer described inconnection with the second form of the wrench shown in Figs. 9 to 12'.

The construction shown in Figs. lf3 to 16'has an advantage over theprior construction in that the single circular contour of the hammer andthe chordal slots in the ends of the hammer are more easily formed thanthe corresponding parts of the'other forms of the hammer. In additionthe hammer 20C is reversibleend Vfor end in the wrench so that in theevent that the edge of the' 'impact rib 19C becomes worn after prolongeduse of the Wrench in one direction of operation the wrench may be` dis`assembled and the hammer reversed to thus present the unworn oppositeedge of the impact rib for `continued use in the wrench.

The form of wrench'illustrated in Figs. 17 to 20 is similar to the Yformof wrench j'ust described and shownv in Figs. 13 to 16. The hammer 20Dis circular as in Figs. 13 to 16 yand coacts with the same type of4anvil 16D. However only one end of the hammer V20D is slotted and theslots 25D are formed along a diameter of thehammer so that 'the axiallyextending vflanges 23D on the drive member 21D are aligned on oppositesides of the coupling portion 22D of the drive member. The `drive memberis illustrated as an integral machined part as distinguished from thetwo piece assembly 21C and 212C in the previous form of the wrench. Thestructure illustrated in Figs 17 to 20 operates in the same manneriasthat illustrated in Figs. 13 to 16 v In all forms of the wrench theinnerportion of the'anvil and the striker rib thereon is desirablyformed ofs'light'ly harder material than the'hammeran'd theimpact ribthereon. This causes any wear or deformation to occur-in the impact ribrather than in the st'rik'erib so that the wrench may be reconditionedwhen necessaryby' installing a-new hammer. However; the wear in thewrenchpartsis Slight because the coating surfaces of theimpact ribandstriker rib are engaged in at parallely relation in a plane normalt'othe path 'of movement of the hammer andy the impact rib. `Theentireimpact force is distributed evenly over the coact'ng surfaces,and' there is no sliding' abrasive act'on at the time of impact.YThesliding disengagement'of the vcoacting faces occurs after the impacthas been delivered to the anvil and the friction force .between thesurfaces is not great during the disengaging vmotion ofthe ribs.

'I have thus described fourl highly practical] fforrs of the wrenchsothat vothers mayepr'oduce tle s're with'- out further disclosure. 'Ihavent attempted t6 showV all possible combinations of elements"and"`fe`a't`es' of" the different forms illustrated or'rnodieatonsthereof as it y is believed that suelvartions a'sfmytfe nesirectmaybemade without departing from the theory of the invention as dened in thefollowing claims.

Having thus described my invention what I claim to be new and desire tosecure by Letters Patent is:

1. An impact wrench comprising, a housing having a motor therein with ashaft extending axially of the housing, an anvil journaled in saidhousing coaxially with said shaft and having a stem projecting from theopposite end of the housing from said shaft, said anvil having an innerportion with an axially extending radially projecting segmental strikerrib along one side, a generally cylindrical hammer embracing said innerportion of said anvil and having an axially extending radially inwardlyprojecting impact rib cooperative with said striker rib, the interioropening in said hammer between the inside of said impact rib and theopposite side of the hammer being slightly wider than the diameter ofthe inner portion ot` said anvil at said striker rib whereby said hammermay move radially to disengage said impact rib radially outwardly fromsaid striker rib andwhereby said striker rib will engage the oppositeside of said hammer from said impact rib to return said hammer andimpact rib radially inwardly to striker rib engaging position, a drivemember rotatably connected to said shaft and having an axially extendingcylindrical flange embracing said hammer, and coacting convergingchordal surfaces formed on said flange and the exterior of said hammerto rotatively drive said hammer, the interior of said ange along adiameter extending between said chordal surfaces being wider than saidhammer to permit radial movement thereof, the

chordal surfaces on said hammer converging away from said impact rib andbeing located on the opposite side of the hammer therefrom.

2. An impact wrench comprising, a housing having a motor therein with ashaft extending axially of the housing, an anvil journaled in saidhousing and having a stem projecting from the opposite end of thehousing from said shaft, said anvil having an inner portion with anaxially extending radially projecting segmental striker rib along oneside, a generally cylindrical hammer embracing said inner portion ofsaid anvil and having an axially extending radially inwardly projectingimpact rib cooperative with said striker rib, the interior opening insaid hammer between the inside of said impact rib and the opposite sideof the hammer being slightly widerv than the diameter of the innerportion of said anvil at said striker rib whereby said hammer may moveradially to disengage said impact rib radially outwardly from saidstriker rib, a drive member rotatably connected to said shaft and havingan axially extending cylindrical fiange embracing said hammer, and

coacting chordal` surfaces formed on said ange and said hammer torotatively drive said hammer, the interior of said flange along adiameter extending between said chordal surfaces being wider than saidhammer to permit radial movement thereof, the chordal surfaces on saidhammer converging away fromsaid impact rib and being located `on theopposite side of the hammer therefrom.

3. An impact wrench comprising, a housing having a shaft extendingaxially of the housing, an anvil journaled in said housing coaxiallywith said Shaft and having a stern projecting from the opposite end ofthe housing from said shaft, said anvil having an inner portion with anaxially extending radially projecting segmental striker rib along oneside, a tubular hammer embracing said inner portion of said anvil andhaving an axially extending radially inwardly projecting impact ribcooperative with said striker rib, the interior opening in said hammerbetween the inside of said impact rib and the opposite side of thehammer being slightly wider than the diameter of the inner portion ofsaid anvil at said striker rib whereby said hammer may move radially todisengage said impact rib radially outwardly from said striker rib andwhereby said striker rib will engage the vopposite side 'of said hammerfrom said impact rib to return said hammer and impact rib radiallyinwardly to striker rib engaging position, a rotatable drive memberdrivingly connected to said shaft and having an axially extendingcylindrical ilange axially overlapping said hammer, and coactingconverging chordal surfaces formed on said flange and the exterior ofsaid hammer to rotatively drive said hammer, the interior of said angealong a diameter extending between said chordal surfaces being widerthan said hammer to permit radial movement thereof, the chordal surfaceson said hammer converging away from said impact rib and being located onthe with said striker rib, the interior opening in said hammer betweenthe inside of said impact rib and the opposite side of the hammer beingslightly wider than the diameter of the inner portion of said anvil atsaid striker rib'whereby said hammer may move radially to disengage saidimpact rib radially outwardly from said striker rib and whereby saidstriker rib will engage the opposite side of said hammer from saidimpact rib to return said hammer and impact rib radially inwardly tostriker rib engaging position, a rotatable drive member drivinglyconnected to said shaft and having axially extending flanges axiallyoverlapping said hammer, and coacting chordal surfaces formed on saidanges and said hammer to rotatively drive said hammer.

5. An imjact wrench comprising, a housing, an anvil journaled in saidhousing and having a stern projecting therefrom, said anvil having aninner portion with an axially extending radially projecting segmentalstriker rib along one side, a tubular hammer embracing said innerportion of said anvil and having an axially extending radially inwardlyprojecting impact rib cooperative with said striker rib, the interioropening in said hammer between the inside of said impact rib and theopposite side of the hammer being slightly wider than the diameterof theinner portion of said anvil at said striker rib whereby said striker ribwill engage the opposite side of said hammer from said impact rib toreturn said hammer and impact rib radially inwardly to striker ribengaging position, a rotatable drive member in said housing and havingan axially extending drive portion axially overlapping said hammer, andcoacting chordal surfaces formed on said drive portion and said hammerto rotatively drive said hammer, said hammer and said drive portionsbeing relatively movable transversely of the axes of rotation thereof topermit radial movement of the hammer.

6. An impact wrench comprising, a housing having a motor therein with ashaft extending axially of the housing, an anvil journaled in saidhousing and having a stem projecting from the opposite end of thehousing from said shaft, said anvil having an inner portion with anaxially extending radially projecting segmental striker rib along oneside, a generally cylindrical hammer embracing said inner portion ofsaid anvil and having an axially extending radially inwardly projectingimpact rib cooperative with said striker rib, the interior opening insaid hammer between the inside of said impact rib and the opposite sideof the hammer beingslightly vwider than the diameter of the innerportion of said anvil at said striker riby whereby said hammer may moveradially to disengage said impact rib radially'outwardly from saidstriker rib, a drive member rotatably connected to said shaft and havingan axially extending ilat surface disposed in chordal relation to theaxis of rotation of said drive member, and a coacting chordalsurface-formed on said hammer to rotatively drive said hammer, saidchordal surfaces extending at an angle of substantially less than 90from a diameter through the rib on said hammer to permit radial movementthereof away from said striker rib.

7. In an impact wrench having a rotatable anvil member and a drivemember rotatable about a fixed axis parallel to the axis of said anvilmember, means forming a driving connection between said memberscomprising, an interior axial portion on one of said members having aradially extending striker rib thereon, axially extending flat drivesurfaces on the other of said members disposed in kchordal relation tothe axis of rotation thereof, and a tubular hammer disposed between saidmembers and around said interior portion, said hammer having an impactrib projecting radially inwardly from the inside thereof and cooperativewith said striker rib, the opening in said hammer being wide enough topermit radial movement of the hammer and the impact rib thereon out ofengagement with said striker rib, said hammer having flat axiallyextending areas formed thereon in chordal re lation cooperative withsaid flat drive surfaces, said flat areas being disposed atsubstantially less than 90 from a diametrical plane passed through saidimpact rib.

8. An impact wrench comprising, a housing having a motor with a shaftdisposed axially of the housing, an anvil journaled in said housingcoaxially with said shaft and having a stem projecting from the housingat the opposite end thereof from said shaft, an inner portion on saidanvil having relatively rotatable centering engagement with said shaft,a tubular hammer embracing the inner portion of said anvil, a radiallyprojecting striker rib on the inner portion of said anvil, a radiallyinwardly projecting impact rib on the inside of said hammer cooperativewith said striker rib, the interior diameter of said hammer at saidimpact rib being slightly greater than the diameter of the inner portionof said anvil at said striker rib whereby said hammer can move radiallyto disengage said impact rib outwardly from said striker rib, a drivemember relatively non-rotatably connected to said shaft and projectingover the end of said hammer, axially turned parallel flanges on the endsof said drive member, both ends of said hammer having parallel chordalslots formed therein parallel to said impact rib with the slots at theend of the hammer adjacent said drive member slidably and drivinglyengaging the flanges on said drive member, said hammer being retainedaxially between said drive member and a flange on said anvil.

9. An impact wrench comprising, a housing having a motor with a shaftdisposed axially of the housing, an anvil journaled in said housing andhaving a stem projecting from the housing at the opposite end thereoffrom said shaft, an'inner portion on said anvil, a tubular hammerembracing the inner portion of said anvil, a radially projecting strikerrib on the inner portion of said anvil, a radially inwardly projectingimpact rib on the inside of sad hammer cooperative with said strikerrib, the interior diameter of said hammer at said impact rib beingslightly greater than the diameter of the inner portion of said anvil atsaid striker whereby said hammer can move radially to disengage saidimpact rib outwardly from said striker rib, a drive member relativelynon-rotatably .connected to said shaft and projecting over the end ofsaid hammer, axially turned parallel flanges on the ends of said drivemember, both ends of said hammer having parallel chordal Slots formedtherein parallel to said impact rib with the slots at the end of thehammer adjacent said drive member slidably and drivingly engaging theflanges on said drive member.

l0. An impact wrench comprising, a housing having a motor with a shaftdisposed axially of the housing, an anvil journaled in said housing andhaving a stem projecting from the housing at the opposite end thereoffrom said shaft, an inner portion on said anvil, a tubular ham--mer'embracing the inner portion of said anvil, a radially projectingstriker rib on the inner portion of said anvil,

a radially inwardly `projecting impact rib on the inside of said hammercooperative with said striker rib, the interior diameter of said hammerat said impact rib being slightly greater than the diameter of the innerportion of said anvil at said striker rib whereby said striker ribengages the inside of said hammer opposite said impact rib to move saidimpact rib inwardly to striker rib engaging position, a drive memberrelatively non-rotatably connected to said shaft and projectingtransversely over the end of said hammer, axially turned parallelflanges on the ends of said drive member, the end of said hammeradjacent said drive member having parallel chordal slots formed thereinparallel to said impact rib with the slots slidably and drivinglyengaging the flanges on said drive member.

l1. An impact wrench comprising, a housing, an anvil journaled in saidhousing, an inner portion on said anvil, a tubular hammer embracing theinner portion of said anvil, -a radially projecting striker rib on theinner portion of said anvil, a radially inwardly projecting impact ribon the inside of said hammer c0- operative with said striker rib, theinterior diameter of said hammer at said impact rib being slightlygreater than the diameter of the inner portion of said anvil at saidstriker rib whereby said hammer can move radially to disengage saidimpact rib outwardly from said striker rib, a drive member rotatablymounted in said housing and projecting transversely of its axis 0frotation over the end of said hammer, axially turned parallel flanges onthe ends of said drive member, the end of said hammer adjacent saiddrive member having parallel chordal slots formed therein parallel tosaid impact rib with the slots slidably and drivingly engaging theflanges on said drive member.

12. An impact wrench comprising, a housing, an anvil journaled in saidhousing, an inner portion on said anvil, a tubular hammer embracing theinner portion of said anvil, a radially projecting kstriker rib on theinner portion of said anvil, a radially inwardly projecting impact ribon the inside of said hammer cooperative with said striker rib, theinterior diameter of said hammer at said iripact rib being slightlygreater than the diameter of the inner portion of said anvil at saidstriker rib whereby said hammer can move radially to disengage saidimpact rib outwardly from said striker rib, a drive member rotatablymounted in said housing and projecting transversely of its axis ofrotation over the end of said hammer, the adjacent ends of said hammerand drive member having a tongue and groove in slidable drivingengagement disposed generally parallel to said impact rib.

13. An impact wrench comprising, a housing having a motor with a shaftdisposed axially within the housing, an anvil journaled in said housingcoaxially with said shaft, an inner portion on said anvil havingrelatively rotatable centering connection with said shaft and having anaxially extending radially projecting striker rib formed along its side,a tubular hammer embracing the inner portion of said anvil and seatedaxially on a flange on said anvil, a radially inwardly projecting andaxially extending impact rib formed on vthe inside of said hammer, thediameter of the inner portion of said anvil at the striker rib thereonbeing slightly less than the interior diameter-of said hammer at `theimpact rib thereon whereby the hammer and impact rib may move radiallyoutwardly from said striker rib, a drive member having a relativelynon-rotatable driving engagement with said shaft and extending acrossthe end of said hammer, a peripheral flange on said drive memberembracing said hammer and rotatively guided by the interior of saidhousing, axially extending converging chordal surfaces formed on saidflange, and corresponding chordal surfaces formed on said hammer andconverging from opposite sides of a diameter drawn through said strikerrib whereby the hammer may move lradially from between said chordalsurfaces on said flange.

14. An impact wrench comprising, a housing having a motor with a shaftdisposed axially within the housing,

an anvil ournaled in said housing coaxially with said shaft, an innerportion on said anvil having relatively rotatable centering connectionwith said shaft and having an axially extending radially projectingstriker rib formed along its side, a tubular hammer embracing the innerportion of said anvil and seated axially on a ange on said anvil, aradially inwardly projecting and axially extending impact rib formed onthe inside of said hammer, the diameter of the inner portion of saidanvil at the striker rib thereon being slightly less than the interiordiameter of said hammer at the impact rib thereon whereby the hammer andimpact rib may move radially outwardly from said striker rib, a drivemember having a relatively non-rotatable driving engagement withsaidshaft and extending across the end of said driving member, a peripheralllange on said drive member embracing said hammer and rotatively guidedby the interior of said housing, axially extending parallel chordalsurfaces formed on said flange, and corresponding chordal surfacesformed on said hammer and positioned on opposite sides of a diameterdrawn through said striker rib whereby the hammer may move radiallybetween said chordal surfaces on said ange.

l5. An impact wrench comprising, a housing having a motor with a shaftdisposed axially within the housing, an anvil journaled in said housing,an inner portion on said anvil having an axially extending radiallyprojecting striker rib formed along its side, a tubular hammer embracingthe inner portion of said anvil, a radially in wardly projecting andaxially extending impact rib formed on the inside of said hammer, thediameter of the inner portion of said anvil at the striker rib thereonbeing slightly less than the interior diameter of said hammer at theimpact rib thereon whereby the hammer and impact rib may move radiallyoutwardly from said striker rib, a drive member having a relativelynonrotatable driving engagement with said shaft and extending across theend of said hammer, said striker rib extending around said anvil throughan are of between 20 and 90 degrees, a peripheral flange on said drivemember embracing said hammer, axially extending chordal surfaces formedon said ange, and corresponding chordal surfaces formed on said hammerand positioned on opposite sides of a diameter drawn through saidstriker rib whereby the hammer may move radially between said chordalsurfaces on said tlange.

16. In an impact Wrench having a rotatable anvil member and a drivemember rotatable about fixed axes, means forming a driving connectionbetween said members comprising, an interior axial portion on one ofsaid members having a radially extending striker rib thereon, drivesurfaces on the other of said members disposed in chordal relation tothe axis of rotation thereof, and a tubular hammer disposed between saidmembers and around said interior portion, said hammer having an impactrib projecting radially inwardly from the inside thereof and cooperativewith said striker rib, the opening in said hammer being wide enough topermit radial movement of the hammer and the impact rib thereon out ofengagement with said striker rib, said hammer having areas formedthereon in chordal relation cooperative with said drive surfaces, saidareas being disposed at substantially less than from a diametrical planepassed through said impact rib.

References Cited in the tile of this patent UNITED STATES PATENTS2,219,883 Amtsber'g Oct. 29, 1940 2,256,496 Robinson Sept. 23, 19412,326,347 Forss Aug. l0, 1943 2,425,793 Fosnot Aug. 19, 1947 2,463,656Thomas Mar. 8, 1949 2,508,997 Fitch May 23, 1950 2,514,914 Van SittertJuly 11, 1950 2,518,049 Mosier Aug. 8, 1950 2,580,607 Schmid Ian. l,1952 2,663,395 Schmid Dec. 22, 1953

